The invention relates to a method for manufacturing a bladed ring for drum-shaped rotors of turbomachinery, especially rotors for axial compressors of gas turbine engines.
A compressor rotor for gas turbine engines is known from German Patent document DE-PS 31 01 250, in which the drum-shaped rotor is assembled from ring elements partly constructed using a stiffening box design. The ring elements are supported against one another at their end faces via center tabs turned toward one another. The tabs engage recesses distributed around the circumference of the ring elements between the blade roots of a rotor blade grid. The rotor blades radially abut both ends of the ring element with hammer-head-shaped root ends. Segments of the ring elements abutting the respective roots of the rotor blades at both ends are designed to serve as supports for reinforcing rings that are fiber-reinforced and extend over the circumference. The following, among other things, are viewed as disadvantageous in this known rotor design:
There is no positive or non-positive material-wise and absolutely firm fiber ring anchoring. Thermal as well as circumferential and radial stresses can lead to undesirable relative movements and loosening of the fiber rings, especially with regard to frequent, non-steady-state, operating conditions, i.e. other fluctuations in load and rotational speed. PA1 There is a design-dictated arrangement for the fiber rings, so that an arrangement of the fiber rings which is individually adjusted to the respective circumferential and radial mass loads that are greatest is not possible. PA1 There is a specific, solid, and heavy blade design. PA1 Replacing a blade, i.e., such as due to damage, requires loosening the ring or drum bond. PA1 The fiber ring is accessible from the outside, and therefore directly exposed to the flow and corresponding temperatures. The ring is thus endangered both by erosion and by foreign particles. PA1 There is formed a bond that is critical in terms of strength, as the consequence of an overlapping loose supporting connection via narrow tongues between the axial root recesses. PA1 There are manufacturing difficulties. The fiber rings must be inserted or shrunk into circumferential grooves while attempting to maintain their self-contained design and structure strength. PA1 Embedding wound rings, made of fibers bonded in a metal matrix, in metal powder; PA1 Performing hot isostatic pressing (HIP) of the system according to the above step; and PA1 Finishing the prefabricated ring blanks to their final dimensions.
There is therefore needed a method for manufacturing a bladed ring by which a lightweight blade ring for a drum-shaped rotor can be produced in a relatively simple fashion with locally directed control of circumferential and radial loads that appear. The manufacturing must be done in such manner that there are no fluidic (high-pressure air/hot gas) or mechanical adverse effects on the fiber rings used.
The present invention meets these needs by providing a method for manufacturing a bladed ring for drum-shaped rotors of turbomachinery, especially rotors for axial compressors of gas turbine engines. The method makes use of the following steps:
Without being tied to a heavy wheel disk design that is expensive to manufacture, a comparatively lightweight rotor design using the drum structure can be produced. In this design, the bladed rings can be welded directly to one another, or by means of intermediate rings or locally by means of ring elements that taper to "shaft stubs," e.g. by frictional or electron beam (EB) welding. The bladed rings, within the scope of the rotational speed and stress due to centrifugal force (circumferential and radial stress), are locally reinforced by the fiber rings. The fiber rings are arranged with their fibers mainly extending in a direction over the circumference. Available as prefabricated "semi-finished products", the fiber rings, in the course of the manufacturing process, are bonded in an absolutely permanent and operationally stable fashion by the hot isostatic pressing process (HIP) into the metal material of the bladed ring. In view of the pressures and temperatures used in HIP, the fiber rings, as far as their metal matrix is concerned, can be permanently connected with the metal material of a bladed ring, supplied in powder form to the HIP, for example, to a metal capsule, by surface diffusion (diffusion welding). The bladed ring blank, which after the HIP process still has excess material with respect to its finished size, can be finished by machining, for example, by turning and/or grinding, to its finished size without damaging the fiber rings.
Within the scope of the present invention, "preliminary manufacture" integral with the ring is possible. In addition, for example, outer root stub prefabrication of depressions, both as to the surface and integral with the ring, extending over the circumference is possible. The depressions are intended to form, in the course of subsequent finishing, axial grooves for the roots of rotor blades that are to be mounted later. With a ring surface completely machined to the required size and root stubs that are completely finished, the blade profiles or blades can be permanently connected by welding, e.g. linear frictional welding, with the respective ring surface or the root stubs.
Another advantage of the method according to the present invention is that the fiber rings are not directly exposed to the process fluid (compressor air, gas, hot gas) so that they are not subjected to any direct fluidic temperature influence or any chemical influence (corrosion) or abrasion, such as by particles in the fluid.
Especially within the framework of the diffusion bonding that is possible with hot isostatic pressing, the same metallic materials, or at least chemically-physically similar material pairs, are provided for the metal powder material of the bladed ring, and also for the metallic matrix of the fiber rings or for the outer metal fiber core coating.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.